Neutral oligosaccharides in human milk samples from approximately 50 women were analysed applying a recently developed high-pH anion-exchange chromatographic method. Three different oligosaccharide patterns could be detected in accordance with milk groups that had been already described. These oligosaccharide groups correspond to the Lewis blood types Le(a-b+), Le(a+b-) and Le(a-b-). In addition to these oligosaccharide patterns, a new carbohydrate pattern was detected in a milk sample from a Le(a-b-) individual. Here, only nonfucosylated oligosaccharides and compounds bearing alpha1,3 linked fucosyl residues were found, whereas structures with alpha1,2 and alpha1,4 fucosyl linkages were missing. This finding led to the hypothesis that there are four different oligosaccharide milk groups that fit well to the genetic basis of the Lewis blood group system.